Prosimians Find a Home Far from Home

In North Carolina, researchers are gaining insight into the behavior of some of the world's most unusual primates

02-01-1998
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Doug Stewart

When you go to the trouble of importing Coquerel's sifakas from tropical Madagascar to a facility in North Carolina, the last thing you want to see is one of the exotic creatures sailing over a fence. That's why Duke University Primate Center recently increased the no-tree zone around some of its outdoor enclosures from 30 feet to 40 feet. Before the modifications, says center director Ken Glander, "the sifakas were popping right over."

On the ground, sifakas are hoppers. In a tree, however, they operate like trapeze artists, but without a trapeze. "These guys reportedly are able to leap 60 feet horizontally," says Glander, also a biological anthropologist and Duke University professor. "I've never seen that, but I've seen them jump 40 feet." In an enclosure behind him, several of the fuzzy, maroon-and-white primates leap nonchalantly from branch to branch while holding their wiry bodies erect and staring at their human visitors.

Rarest of all sifakas is the golden-crowned species, of which anywhere from 1,000 to 10,000 may exist, but nobody knows for sure. The Duke primate center has the only mating pair in captivity--"our crown jewels," says Glander. Their tiny home range, a patch of forest in Madagascar barely 30 miles square, is the site of a recent gold strike, and miners unfortunately have taken to hunting the animals for food. Duke plans to mount a joint rescue mission with the Malagasy government to bring back more pairs as soon as possible. Their progeny could return once the gold rush peters out.

Helping to keep sifakas and other endangered prosimians from disappearing for good is the Duke facility's primary mission. Hidden in the wilds of Duke Forest near downtown Durham, the center is home to the largest captive population of endangered primates in the world. All are prosimians, members of the oldest living branch of the primate family tree, a suborder of its own. The other primate suborder, the anthropoids, includes monkeys, apes and humans. Most prosimians at Duke are native to Madagascar, where slash-and-burn agriculture, charcoal-making, logging, livestock raising and erosion have drastically shrunk tropical-forest habitat. Of the 21 species represented here, 16 are listed by IUCN--The World Conservation Union as endangered. The center also hosts a half-dozen less-threatened species.

Like the sifakas, many of the other prosimians now thriving at Duke also may one day help restock their ancestral wilderness homes. The facility is more than a breeding station, however. Despite a humble $900,000 annual budget, the private nonprofit center has quietly grown since its founding in 1966 into a major scientific center.

"We're considered to be the world authority on prosimians. When people in zoos have questions, they come to us for answers," says Glander. "Of course, we don't always have them." Research here is largely noninvasive, and even blood samples are taken sparingly. "We do research to benefit the animals, not humans--at least not directly," he adds. The indirect benefit to humans is a better understanding of our own mysterious origins. All modern primates are related to long-ago prosimians (hence their name, meaning "pre-monkey"). "Today's prosimians are really a window on the past," says Glander. As he talks, ring-tailed lemurs festoon a branch on the other side of a fence topped with electrified wire. As they creep, jump and chatter, their bushy striped tails curl and uncurl like animated barber poles.

Compared to monkeys and apes, prosimians have smaller brains, less dextrous fingers and a greater reliance on smell. Prosimians divide into several subgroups. Lorises and galagos inhabit tropical forests of Asia and Africa. Tarsiers are native to the Philippines and other parts of East Asia. Lemurs are native only to Madagascar.

The largest and most plentiful animals at Duke are the lemurs. As they squat in the trees, the larger lemurs like the ring-tailed and the red-fronted could sooner be mistaken for raccoons than relatives of chimps. The black-and-white ruffed lemur, with its long snout protruding from a pouf of white fur, calls to mind a tree-climbing poodle.

The center's nocturnal species occupy indoor cages during the colder months. In one, an aye-aye mother and infant peer down placidly from a branch. Their bulging orange-yellow eyes, beaverish teeth, coarse opossumlike fur and big ears suggest a koala crossed with a squirrel. A slender loris maneuvering around another enclosure calls to mind a rat on stilts.

Nearby, a slow loris has just woken up. It languidly stretches one hand toward a branch, grasps it and begins pulling itself over. No, it's not still sleepy, Glander says. "That's top speed for a slow loris." Sluggishness is a defense: The loris avoids attracting attention. Another novel defense is practiced by the potto, which curls itself into a ball so that a row of unusually sharp vertebrae protrude at the back of its neck. If a weasel or other predator bites down, the vertebrae often will penetrate the roof of the predator's mouth. The potto, of course, is dead at that point, but the predator learns to avoid others.

Glander, an expert on the diets of wild primates, is especially intrigued by the center's bamboo-eating lemurs. These were thought to be extinct after 1900--until a French naturalist found a live one for sale in 1964 in a village market in Madagascar. Like pandas (which they resemble somewhat), bamboo-eating lemurs eat virtually nothing else. To make the best use of the island's limited stands, each of three species of bamboo lemur munches on a different part of the plant: One eats the stalk, another the leaves, a third the green shoots. No other animal eats the shoots, which are laden with cyanide. "The golden bamboo lemur eats enough cyanide every day to kill a person several times over," Glander says. He assumes the animal's diet has medicinal benefits, but he hasn't worked out what those might be.

Duke's captive-breeding program is more sophisticated than the laissez-faire approach that most zoos took as recently as 20 years ago. "In the old days, a male in a zoo might be a really good breeder, so the zoo would breed him a lot and sell his offspring to a lot of other zoos," says Barbara Coffman, a former research associate at the Duke center. For endangered animals, this strategy resulted in genetic sameness that left a species ill-equipped to cope with new diseases or environmental changes.

Now Duke and other breeding facilities have joined forces to keep exhaustive genealogies of their captives, tracing the animals' bloodlines back to wild-caught forebears. Coordinated by the IUCN, a detailed Species Survival Plan sets breeding guidelines for each of 134 endangered species, from black rhinos to pygmy lorises. Prospective mates or their sperm are shipped from zoo to zoo as needed. The overriding consideration is to keep each population's genetic deck as well shuffled as possible, generation after generation.

For behavioral scientists Duke's roomy, natural-habitat enclosures are a passable substitute for true field conditions. Ken Glander refers to the colony of lemurs in the largest, 23-acre enclosure as "almost free-ranging." In Madagascar, the same group would roam at most 200 acres. "You can study group dynamics in Madagascar, but you can't get as close to the animals," says Glander. "Here, they don't get spooked by humans. And we have 30 years of genetic history on some of these animals. All this means we can get much more information in a much shorter time."

One of the information gatherers is Frances White, a behavioral ecologist. She has been studying lemurs here for more than 10 years, especially larger diurnal animals like ruffed lemurs and ring-tails. One of the unusual characteristics of lemur society she is studying is female dominance. "Female lemurs get the best food. They do much of the mate choice. Males are often deferent." She hypothesizes that the females' dominance serves to ensure their young are well nourished despite limited resources. In ongoing experiments, males seem to lose their deference when food is widely available.

Like Darwin's finches, Madagascar's lemurs have evolved in remarkably distinctive ways. Consider the aye-aye's middle finger: Thin and knobby, it can bend almost snakelike in any direction. The animals use it for everything from tapping for grubs to splashing water into their mouths. In the wild, this appendage has almost been the species' undoing. "Many villagers in Madagascar think aye-ayes can put curses on them," says Carl Erickson, a Duke experimental psychologist. "They think that if an aye-aye points its weird middle finger at you, you have to kill it to lift the curse."

Superstition, compounded by habitat loss, has nearly wiped out the aye-aye in the wild. No one knows how many remain in Madagascar's shrinking forests. Until recently, the species was considered on the verge of extinction, but lately several small and widely scattered pockets of aye-ayes have turned up on the island. Even so, the aye-aye may be the most endangered primate in the world.

Erickson's fascination with aye-ayes began when the first aye-aye arrived at Duke in the late 1980s. "He had his nose down over a piece of galvanized pipe in his enclosure, his ears were forward and he was tapping on the pipe with that bizarre middle finger," Erickson recalls. He guessed the aye-aye had mistaken the pipe for a tree branch and was tapping it to find insects. In a series of experiments since then, Erickson has proved his hunch correct: Aye-ayes listen to the tapping with their huge ears to locate cavities likely to contain prey. "If we're going to be the custodian of this species," he says, "it's important that we don't let skills like this deteriorate over generations."

Luckily, captive-born animals seem to inherit at least some survival skills. In a test, a Doberman pinscher was walked outside a fence containing captive-born lemurs. The animals climbed high into the trees and gave the ground-predator cry. When large birds have flown overhead, the lemurs have given the aerial-predator call and dropped down to the lower branches, just as wild lemurs do. "They have an instinctive reaction to these things," says Glander. "It's totally hard-wired."

The real test is now underway. Last fall, Duke and Malagasy scientists for the first time released captive-bred prosimians into the wild--five radio-collared black-and-white ruffed lemurs. A second group of lemurs will join them later this year. Old World primates have never been successfully reintroduced to the wild before, but Glander is confident. "I'm convinced this will work. In fact, I know it will work. But we have to convince the world."

Freelancer Doug Stewart, being unsuperstitious, is proud to be a distant relative of the aye-aye.